This invention relates to multi-component mixing assemblies and more particularly to a pneumatically operated, portable, chemically interactive resin and catalyst liquid mixing and dispensing assembly which may be operated in the field under a variety of ambient conditions while maintaining precision ratioing of the liquid components under a variety of ambient temperature and physical conditions. It is particularly adapted for repairing concrete structures.
The restoration of cracked concrete structures by resin injection is an alternative to complete replacement. It can produce remarkable cost savings. A crack or void in a concrete structure is a sign of failure caused by one or more problems such as for example stresses, inadequate design, improper curing, shifting of substrata, etc. A structural crack may produce an effect on the reinforcing bar or bars in a concrete structure. The reinforcing bars can represent an important part of the structural value of the concrete. Unrepaired cracks permit entry of, for example, moisture, road salts, and other contaminants for attack of the rebar and as a result, the structure may be lost.
The injection of chemically curable resins has two important effects, mainly it seals the crack to prevent damaging moisture entry, and secondly it monolithically welds the structure together. While it is often assumed that the welding of the structure is the most important result of the repair--the sealing properties of the repair are equally important, since they prevent further deterioration of the reinforcing bars.
It will be appreciated that concrete structures vary widely in size, location and in use or application. Thus, repair situations encountered in the field vary widely also.
One presently used method of repairing cracks involves the steps of drilling ports at spaced intervals along a crack or cracks in the area to be repaired, placing a sealing mix of epoxy along the external portions of the cracks, sealingly inserting injection entry tubes into the drilled ports, filling the ports through the tubes with water to flush out any dirt and debris from the cracks and then injecting freshly mixed resin and catalyst under pressure into the ports to fill the voids and the cracks while forcing the water out of the cracks and voids.
It is usual when drilling the ports to use a vacuum type hollow drill bit so that drilling dust does not contaminate the area. The injection or entry tubes may be made of copper and cemented into place in the drilled ports with a sealing mix of resin.
Deterioration of concrete may take various forms which may vary from extremely tiny cracks to relatively large voids spread over large areas. Typical of the latter type of deterioration is delamination of a concrete roadbed along the plane of the reinforcing bars. This requires the drilling of a plurality of vertical ports into the surface of the roadbed and into the void space produced by the delamination. The ports permit flushing of the void space with water and subsequent filling thereof with resin to monolithically bond the separated lamina together.
As aforementioned, field conditions vary widely. However, apparatus affording the flexibility required to maintain precision mixing of the resin and catalyst components under such widely variable conditions has not heretofore been available. The field conditions encountered may vary from pumping of mixed resin and catalyst against a head of water pressure or into voids of such size so as to offer no resistance, or to large cracks or cracks which may be measured in ten-thousandths of an inch. While resins and catalysts are available which will cure well under a variety of conditions, apparatus which is designed to handle a variety of different resins while maintaining exacting proportionality of resin and catalyst have not been heretofore available. Further, the viscosity of the resins and the catalysts vary inversely with temperature, but not to the same extent. Heretofore the pumping mechanisms have not been such as to assure the correct ratio of mixing in a positive manner to accommodate a large range of temperatures encountered in outdoor areas typical of concrete structures.
Typically, prior art mixing and dispensing apparatus such as shown in Roeser U.S. Pat. No. 3,802,805 for multicomponent interactive liquid resins and catalysts are designed to be operated under relatively uniform ambient conditions of temperature and atmospheric pressure at a fixed location in a work place such as a factory or the like. Such apparatus essentially include an air driven cycling reciprocating actuator which drives a separate pump for each of the components which are mechanically linked for simultaneous actuation for delivery of the components to a mixing head. As shown in the Roeser patent, the linkage may be adjustable for varying the ratios of the separate pumps and the separate liquid components may be fed to the pumps by gravity or air pressure. However the separate pumps for the liquid components shown therein are double action pumps in the sense that they are driven from both the filled to discharge position and from the discharged to filled position by a double action driving actuator. Alternatively a so-called single action driving actuator which is driven in one direction but uses a spring bias return is well known. In such prior art apparatus, the return of the actuator during the refill cycle under power or spring bias does not normally provide refill problems at a factory work station because the component liquids that are being pumped have relatively constant viscosities. Thus the "head" pressure or supplied pressure on the liquid components to be pumped can be relied upon to force the components into the liquid pumps in the refill cycle as the driving actuator is being returned and required precise ratioing at the mixing nozzle occurs. Such prior art devices become unreliable when encountering the diverse ambient fluctuating conditions typical of outdoor concrete installations such as roadbeds, bridges, underground sewers, dams, parking structures, etc. which vary widely in ease of access, physical environment, locational elevation and temperature variations.
For example, many typical liquid epoxy resin and catalyst components are chemically formulated for nearly identical viscosity at approximately 68.degree.-70.degree. F. However, typically while both the component liquids become more viscous with temperature drop (vary inversely with temperature), the liquid resin component becomes substantially more viscous than the liquid catalyst component. Thus at low temperatures and/or pressures, an apparatus using a double action driving mechanism or a spring return mechanism may return the pump to the "filled" position but the viscous resin has not in fact filled its respective pump chamber to the same extent that the catalyst pump chamber has been filled, and a resin short mixture is pumped from the mixing dispensing nozzle. This condition, it will be appreciated, is especially deleterious in attempted repair of internal cracks and voids in concrete structures since once mixed (even through poorly) the process is irreversable.
Also, the known prior art devices do not control flow volume at the mixing dispensing head independent of the pressure at the mixing dispensing head. In repair of tiny cracks, high pressure low volume is often desired since high volume high pressure attempted repair may provide an undesired hydraulic jack effect to the structure being repaired.
One known advertisement for a commercial assembly for mixing and dispensing liquid epoxy and catalyst used for repair of concrete structures is shown in a September 1979 bulletin of Rocky Mountain Chemical Company of Casper, Wyo. 82601, entitled Niklepoxy Injection Machine. While advertised that it "can be easily transported by one man", the unit weighs 90 pounds (presumably with empty tanks) and essentially comprises an open box like frame with all the component tanks, pumps, driving mechanism and gauges disposed therewithin. The assembly appears to be essentially similar in gross to Roeser U.S. Pat. No. 3,802,805 except for being placed in a rectilinear box, does not appear to have adjustability of ratios, and is designed for normal low pressure injection of approximately 20 psi. Neither this or the Roeser prior art assemblies are in fact easily portable, they have mechanical linkages, seals and other moving parts exposed to the environment when operating, and they have other deficiencies which will become more apparent in the discussion below.
More particularly, the prior art devices above described suffer one or more of the following deficiencies which the instant assembly successfully surmounts for effectively overcoming field problems previously discussed:
(a) The prior art devices do not rely upon the hydraulic filling of positive displacement pneumatically driven at selectively adjustable pressure pumps so arranged that the higher viscosity liquid resin component must hydraulically contribute to the moving of the pump driving mechanism from its pumped out toward its pump refill position; PA1 (b) The mechanisms and pneumatic circuits of the prior art are not assured of correctly proportioned pump-outs of the separate liquid components on stop and restart in mid pumping cycle at all viscosity levels of the components; PA1 (c) The prior art devices do not have an operator controllable adjustable flow rate of discharged mixed components which is totally independent of the selectively adjustable pressure at which they are discharged in mixed relation, the flow pressure being at a separately adjustable pressure over a varied and operator selectable pressure range below 20 psi to above 250 psi to afford a selection of high to low volume pumping over a range of high to low pressures to provide versatility for widely divergent field conditions; PA1 (d) The prior art devices do not have high limit pressure protection controls on the apparatus which automatically recycles the apparatus for either work encountered or malfunctioning encountered blockages downstream of the pumping mechanism to protect from conduit bursting or abnormal strains on the moving parts and consequent damage while permitting the continuous pumping at the high pressure limit which may be encountered in certain field conditions; PA1 (e) Prior art devices do not have the liquid components pressurized holding tanks physically and shieldingly separated from the control mechanisms, the driving mechanisms and the pumping mechanisms whereby operator refilling spills which may gum up these mechanisms are obviated as a problem and additionally the holding tanks are not easily accessible and quickly releaseably held to a frame for refilling apart from the rest of the assembly; PA1 (f) The prior art devices are not so arranged and disposed such that the pump driving mechanisms, the pumps, the valving mechanisms and the other moving parts and controls are disposed in an internal chamber of an elongated rugged housing so as to be protected against dirty environmental conditions during the field use of the apparatus, but with external manually operated controls for easy operation; PA1 (g) The prior art devices are not readily movable on a job site on wheels by a single operator and are not readily movable through a 22 inch standard manhole while maintained in an upright relationship; PA1 (h) The prior art devices are not provided with a rugged handle means on a rugged frame housing means for a multicomponent liquid mixing and dispensing apparatus so disposed and arranged as to provide easy tilting and moving of the assembly on the job site by a human operator and simultaneously provide a convenient attachment point for easy lifting or lowering thereof by a small hoisting mechanism, the frame housing means being able to withstand the rigors of normal construction equipment type use while protecting the delicate and precision components there within.
The apparatus described below overcomes the enumerated deficiencies and provides a rugged compact movable assembly which is of high quality, durability, versatility, easy to manufacture and assemble, high precision, provides reliable mixing and dispensing for a wide range of applications, and may be operated by relatively unskilled operators with minimal instruction.